Source: Kaplan GED Test Prep 2022–2023 by Caren Van Slyke Authority Tier: Commercial Preparation (
TIER_3_COMMERCIAL) | License: Restricted Reference (RESTRICTED) Coverage: Chapter 4: Physical Science (Pages 1198–1221) Curriculum Standard: High School Equivalency Preparation
Kaplan Reference: Chapter 4: Physical Science
Lesson 1: Atoms and Molecules
(Page 1198)
CHAPTER 4 Physical Science Lesson 1: Atoms and Molecules Key Ideas Atoms are formed of positively charged protons, neutral neutrons, and negatively charged electrons. All matter can be classified as elements, compounds, or mixtures. Atoms are held together in molecules and compounds by bonds. All matter is made of tiny particles called atoms. An atom is the smallest unit of matter that can combine chemically with other matter and that cannot be broken down into smaller particles by chemical means. Atoms are themselves made of subatomic particles . The major subatomic particles are protons, neutrons, and electrons. Protons are particles with a positive charge, and neutrons are particles with no charge. Together, protons and neutrons form the nucleus of all atoms except hydrogen, which has just one proton in its nucleus. Electrons are particles with negative charge. Electrons orbit the nucleus of an atom. When an atom has an equal number of protons and electrons, it is electrically neutral. When an atom gains or loses electrons, it